Sierra University operated during the 1980's and early 1990s in California. At the time, the state had a "three tier" system.
At the lowest level, "Authorized," schools were allowed to operate after sending in an application with an affadavit attesting to their compliance in 13 specific areas, and that they had at least $50,000 in assets dedicated to the school. The second level was "Approved."
At that time, California approved individual degree programs within schools, rather than whole schools. So, you could have a school with most of its programs Authorized, yet have one or more programs Approved.
The third category was "Accredited," meaning the school was accredited by a USDOE-recognized agency.
Sierra University's degree programs were all Approved.
Sierra went out of business sometime during the early 1990s, as did many small graduate schools of psychology in California. According to the California Dept. of Education, the keeper of records for the defunct Sierra, is the San Diego University for Integrative Studies, 3900 Harney Street, Suite 210 San Diego, CA 92110.